Home About us Contact
|
Home About us Contact | ||
|
|
||
Hz Band (hz + band)
Selected AbstractsNeuropathic pain in spinal cord injury: significance of clinical and electrophysiological measuresEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2009Susanne Wydenkeller Abstract A large percentage of spinal cord-injured subjects suffer from neuropathic pain below the level of the lesion (bNP). The neural mechanisms underlying this condition are not clear. The aim of this study was to elucidate the general effects of spinal deafferentiation and of bNP on electroencephalographic (EEG) activity. In addition, the relationship between the presence of bNP and impaired function of the spinothalamic tract was studied. Measurements were performed in complete and incomplete spinal cord-injured subjects with and without bNP as well as in a healthy control group. Spinothalamic tract function, assessed by contact heat evoked potentials, did not differ between subjects with and without bNP; nevertheless, it was impaired in 94% of subjects suffering from bNP. In the EEG recordings, the degree of deafferentiation was reflected in a slowing of EEG peak frequency in the 6,12-Hz band. Taking into account this unspecific effect, spinal cord-injured subjects with bNP showed significantly slower EEG activity than subjects without bNP. A discrimination analysis in the subjects with spinothalamic tract dysfunction correctly classified 84% of subjects as belonging to either the group with bNP or the group without bNP, according to their EEG peak frequency. These findings could be helpful for both the development of an objective diagnosis of bNP and for testing the effectiveness of new therapeutic agents. [source] Oscillatory activity in parietal and dorsolateral prefrontal cortex during retention in visual short-term memory: Additive effects of spatial attention and memory loadHUMAN BRAIN MAPPING, Issue 10 2009Stéphan Grimault Abstract We used whole-head magnetoencephalography to study the representation of objects in visual short-term memory (VSTM) in the human brain. Subjects remembered the location and color of either two or four colored disks that were encoded from the left or right visual field (equal number of distractors in the other visual hemifield). The data were analyzed using time-frequency methods, which enabled us to discover a strong oscillatory activity in the 8,15 Hz band during the retention interval. The study of the alpha power variation revealed two types of responses, in different brain regions. The first was a decrease in alpha power in parietal cortex, contralateral to the stimuli, with no load effect. The second was an increase of alpha power in parietal and lateral prefrontal cortex, as memory load increased, but without interaction with the hemifield of the encoded stimuli. The absence of interaction between side of encoded stimuli and memory load suggests that these effects reflect distinct underlying mechanisms. A novel method to localize the neural generators of load-related oscillatory activity was devised, using cortically-constrained distributed source-localization methods. Some activations were found in the inferior intraparietal sulcus (IPS) and intraoccipital sulcus (IOS). Importantly, strong oscillatory activity was also found in dorsolateral prefrontal cortex (DLPFC). Alpha oscillatory activity in DLPFC was synchronized with the activity in parietal regions, suggesting that VSTM functions in the human brain may be implemented via a network that includes bilateral DLPFC and bilateral IOS/IPS as key nodes. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] Oscillations in the basal ganglia under normal conditions and in movement disordersMOVEMENT DISORDERS, Issue 10 2006Plamen Gatev MD Abstract A substantial body of work within the last decade has demonstrated that there is a variety of oscillatory phenomena that occur in the basal ganglia and in associated regions of the thalamus and cortex. Most of the earlier studies focused on recordings in rodents and primates. More recently, significant advances have been made in this field of research through the analysis of basal ganglia field potentials recorded from implanted deep brain stimulation electrodes in the basal ganglia of human patients with Parkinson's disease and other disorders. It now appears that oscillatory activity may play a significant role in the pathogenesis of these diseases. The most significant finding is that in Parkinson's disease synchronized oscillatory activity in the 10- to 35-Hz band (often termed ",-band") is prevalent in the basal ganglia,thalamocortical circuits, and that such activity can be reduced by dopaminergic treatments. The entrainment of large portions of these circuits may disrupt information processing in them and may lead to parkinsonian akinesia (and perhaps tremor). Although less firmly established than the role of oscillations in movement disorders, oscillatory activities at higher frequencies may also be a component of normal basal ganglia physiology. © 2006 Movement Disorder Society [source] Is the rhythm of physiological tremor involved in cortico-cortical interactions?MOVEMENT DISORDERS, Issue 4 2004Jan Raethjen MD Abstract The function of low-frequency oscillations as correlates of physiological tremor in supplementary motor area (SMA) and M1 remains unclear. In epicortical recordings from M1 and SMA and surface electromyographic (EMG) recordings in an epileptic patient we found reproducibly significant coherence between all three recording sites in the 6- to 15-Hz band. The partial coherence between SMA and muscle, however, was not significant. There was a constant phase shift between SMA and M1 indicating synchronized activity. We conclude that the cortical correlates of physiological tremor may be involved in linking different cortical motor centers and might therefore play a role in cortical motor planning. © 2003 Movement Disorder Society [source] Non-linear EEG synchronization during observation: Effects of instructions and expertisePSYCHOPHYSIOLOGY, Issue 5 2010Claire Calmels Abstract The aim of this study was to examine the effects of instructions and expertise upon neuronal changes during observation of sequential finger movements. Professional pianists and musically naïve subjects observed these movements with the aim of either replicating or recognizing them at a later stage. A non-linear measure of functional coupling was used to investigate EEG activity. In the 10,13 Hz frequency band and in musically naïve subjects, functional coupling during observation for replica was greater within central and neighboring areas than during observation for recognition. An opposite pattern was found in the 4,8 Hz frequency band. In the 10,13 Hz band and in areas including the parietal cortex, functional coupling in musically naïve subjects was greater compared to professional pianists under observation for replica. Results are discussed in the light of recent findings from the cognitive and behavioral neuroscience literature. [source] Effects of 2G and 3G mobile phones on human alpha rhythms: Resting EEG in adolescents, young adults, and the elderly,BIOELECTROMAGNETICS, Issue 6 2010R.J. Croft Abstract The present study was conducted to determine whether adolescents and/or the elderly are more sensitive to mobile phone (MP)-related bioeffects than young adults, and to determine this for both 2nd generation (2G) GSM, and 3rd generation (3G) W-CDMA exposures. To test this, resting alpha activity (8,12,Hz band of the electroencephalogram) was assessed because numerous studies have now reported it to be enhanced by MP exposure. Forty-one 13,15 year olds, forty-two 19,40 year olds, and twenty 55,70 year olds were tested using a double-blind crossover design, where each participant received Sham, 2G and 3G exposures, separated by at least 4 days. Alpha activity, during exposure relative to baseline, was recorded and compared between conditions. Consistent with previous research, the young adults' alpha was greater in the 2G compared to Sham condition, however, no effect was seen in the adolescent or the elderly groups, and no effect of 3G exposures was found in any group. The results provide further support for an effect of 2G exposures on resting alpha activity in young adults, but fail to support a similar enhancement in adolescents or the elderly, or in any age group as a function of 3G exposure. Bioelectromagnetics 31:434,444, 2010. © 2010 Wiley-Liss, Inc. [source] Analyzing digital vector waveforms of 0,3000,Hz magnetic fields for health studies,BIOELECTROMAGNETICS, Issue 5 2010Joseph D. Bowman Abstract To improve the assessment of magnetic field exposures for occupational health studies, the Multiwave® System III (MW3) was developed to capture personal exposures to the three-dimensional magnetic field vector B(t) in the 0,3000,Hz band. To process hundreds of full-shift MW3 measurements from epidemiologic studies, new computer programs were developed to calculate the magnetic field's physical properties and its interaction with biological systems through various mechanisms (magnetic induction, radical pair interactions, ion resonance, etc.). For automated calculations in the frequency domain, the software uses new algorithms that remove artifacts in the magnetic field's Fourier transform due to electronic noise and the person's motion through perturbations in the geomagnetic field from steel objects. These algorithms correctly removed the Fourier transform artifacts in 92% of samples and have improved the accuracy of frequency-dependent metrics by as much as 3300%. The output of the MwBatch software is a matrix of 41 exposure metrics calculated for each 2/15,s sample combined with 8 summary metrics for the person's full-period exposure, giving 294 summary-exposure metrics for each person monitored. In addition, the MwVisualizer software graphically explores the magnetic field's vector trace, its component waveforms, and the metrics over time. The output was validated against spreadsheet calculations with pilot data. This software successfully analyzed full-shift MW3 monitoring with 507 electric utility workers, comprising over 1 million vector waveforms. The software's output can be used to test hypotheses about magnetic field biology and disease with biophysical models and also assess compliance with exposure limits. Bioelectromagnetics 31:391,405, 2010. © 2010 Wiley-Liss, Inc. [source] EEG synchronization in mild cognitive impairment and Alzheimer's diseaseACTA NEUROLOGICA SCANDINAVICA, Issue 2 2003C. J. Stam Objectives , To compute the synchronization likelihood of multichannel electroencephalogram (EEG) data in Alzheimer (AD) patients, subjects with mild cognitive impairment (MCI) and subjects with subjective memory complaints (SC). Material and methods , EEGs (200 Hz sample frequency; 21 channels; average reference) were recorded in 10 AD patients (two males; age 76.2; SD 9.36; range 59,86), 17 subjects with MCI (eight males; age 77.41; SD 6.25; range 62,88) and 20 subjects with SCI (11 males; age 68.9; SD 12.96; range: 51,89). The synchronization likelihood, a novel type of coherence measure, was computed, comparing each channel with all other channels, for the 2,6, 6,10, 10,14, 14,18, 18,22 and 22,50 Hz band. Results , The synchronization likelihood was significantly decreased in the 14,18 and 18,22 Hz band in AD patients compared with both MCI subjects and healthy controls. Lower beta band synchronization correlated with lower Mini-Mental state examination (MMSE) scores. Conclusion , Loss of beta band synchronization occurs early in mildly affected AD patients and correlates with cognitive impairment. [source] | |||||||||||||